import numpy as np
from matplotlib import pyplot as plt


def test():
    #
    start = 0
    end = 20
    x = np.linspace(start, end)
    print(type(x), x)

    #
    y1 = 2 * x - 1
    y2 = x
    y3 = x ** 2

    #
    plt.plot(x, y1)
    plt.plot(x, y2)
    plt.plot(x, y3)

    #
    plt.show()
